3GPP is currently investigating enhancement of machine type device communication (MTC) for release 12.
One category of machine type devices are defined as only requiring “infrequent communication”, that is, they only communicate very seldom, e.g. one or a few IP packets a week or a month. The number of this type of devices can be huge, several times more than the normal type of terminals in the network. Therefore using normal network procedures for these devices may require disproportional large amount of network resources and hence optimizations are needed. Optimizations are also needed to avoid the risk of network overloading from these large numbers of devices.
The requirement from operators is to reduce the resource usage for devices that only communicate very rarely and stay silent for long times. In particular it can be noted that maintaining the default PDN connection in EPS networks is seen as a costly resource usage. But the optimization is of course also needed for devices with more than one (the default) PDN connection.
Some operators have suggested to establish the PDN connection and allocate resources in the PGW and SGW only at the rare occasions when communication from or to these type of devices is actually done. In this way, no memory resources or other resources are allocated in the PGW and SGW at all, and no mobility (MM) related signaling is required between the MME and SGW/PGW when the devices are moving. By keeping the devices attached (registered) in the network, the devices can be reached in case of mobile terminated (MT) communication e.g. from an SCS/MTC Server.
There are some requirements specified in stage 1 document, TS 22.368: “The system shall provide mechanisms to efficiently maintain connectivity for a large number of MTC Devices.” and “MTC Devices may keep their data connection or not keep their data connection when not communicating, depending on operator policies and MTC Application requirements.”
Another feature that is also being discussed in 3GPP SA2 is a new UE state mode, a so-called sleep mode. When a UE is in sleep mode, the UE may not be immediately reachable by the network. It would only be reachable when the device wakes up and does some signaling to the network, e.g. in conjunction to the periodic tracking area update (TAU) signaling (i.e. the periodic “keep alive” signaling in 3GPP networks). Devices using the UE sleep mode state will probably not communicate very often and are likely to be good candidates for belonging to the “infrequently communicating” devices, and hence benefit from the optimization proposed in this invD.
The problem with infrequently communicating devices in LTE networks is that the LTE standard is defined to use the “always connected” paradigm. That is, an attached LTE device does always have a PDN connection. And that will consume resources and create signaling in the network as described above.